Holographic optical elements for augmented reality devices and methods of manufacturing and using the same

ABSTRACT

Holographic optical elements for augmented reality (AR) devices and methods of manufacturing and using the same are disclosed. An example AR device includes a holographic optical element (HOE) including a recorded optical function, and a projector to emit light toward the HOE. The HOE reflects the light based on the optical function to produce a full image corresponding to content perceivable by a user viewing the reflected light from within an eyebox. A first portion of the content is viewable from a first location within the eyebox. A second portion of the content is viewable from a second location within the eyebox. The first portion including different content than the second portion that is non-repeating between the first and second portions.

FIELD OF THE DISCLOSURE

This disclosure relates generally to augmented reality and, moreparticularly, to holographic optical elements for augmented realitydevices and methods of manufacturing and using the same.

BACKGROUND

Augmented reality (AR) involves the integration of computer-generatedperceptual information with a user's perception of the real world. Manyexisting AR systems include head-mounted displays and/or other systemsthat are relatively bulky or cumbersome because of the components neededto generate the computer-generated perceptual information at sufficientspeeds and with a sufficient field of view and resolution desired forthe particular application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a prior AR system with a holographic optical element(HOE) including an optical function recorded therein.

FIG. 2 illustrates an example AR system with an example HOE including adifferent example optical function.

FIG. 3 illustrates another example AR system with an example HOEincluding another example optical function.

FIG. 4 illustrates another example AR system with an example HOEincluding another example optical function.

FIG. 5 illustrates the field of view achieved using the example ARsystem of FIG. 4.

FIG. 6 illustrates an example system to record an example opticalfunction into an example HOE to implement the example AR systems ofFIGS. 2-4.

FIG. 7 illustrates another example system to record an example opticalfunction into an example HOE to implement the example AR systems ofFIGS. 2-4.

FIG. 8 illustrates an example AR device including one or more of theexample AR systems of FIGS. 2-4.

FIG. 9 is a flowchart representative of example machine readableinstructions which may be executed to implement the example AR systemsof FIGS. 2-4.

FIG. 10 is a flowchart representative of an example process to record anoptical function in an unprocessed HOE to manufacture the example HOEsof FIGS. 2-4.

FIG. 11 is a block diagram of an example processor platform structuredto execute the instructions of FIG. 9 to implement the AR device of FIG.8.

The figures are not to scale. In general, the same reference numberswill be used throughout the drawing(s) and accompanying writtendescription to refer to the same or like parts.

DETAILED DESCRIPTION

In current wearable augmented reality (AR) glass solutions, a tradeoffalways exists between the optical engine size (e.g., the size ofcomponents that generate the light to produce a user-perceived image),eyebox size, field of view (FOV), and resolution. Furthermore, manycurrent AR solutions cannot be implemented in normal eyewear (e.g.,prescription glasses, sunglasses, etc.) with curved lenses andrelatively small frames because such existing AR solutions require flatglass lenses (and/or panel displays), bulky “bug eye” style opticalcombiners (e.g., combining prisms and/or flat waveguide combiningoptics), and/or components with form factors that cannot be concealedwithin the frames designed for most normal eyewear.

However, there are some solutions that involve an optical engine basedon a microelectromechanical system (MEMS) scanner that is sufficientlysmall to fit on the frame of normal eyewear. Furthermore, the MEMSscanner may be implemented in conjunction with a holographic opticalelement (HOE) (also referred to as a holographic combiner) that iscurved in a manner corresponding to the curvature of lenses used innormal eyewear. The holographic combiner reflects light from the MEMSscanner towards a user's eye to enable the user to perceive an imagerepresented by the reflected light. For a user to perceive the image,the user's eye needs to be positioned within a particular locationrelative to the HOE so that the reflected light enters the pupil of theuser's eye. The location in which a user's pupil must be located toperceive the reflected image is referred to herein as the eyebox.

In some implementations of this approach, the image projected by theMEMS scanner and reflected by the HOE is relatively small, which resultsin a relatively small eyebox. That is, the user's eye must be in arelatively precise position to perceive the image. It is possible toincrease the effective or overall eyebox size for such AR systems bygenerating an array of multiple separate eyeboxes corresponding tomultiple instances of the image to be perceived by users. In thismanner, as users move their eye, their pupil will remain in at least oneeyebox to maintain visibility of the reflected image. The multipleeyeboxes may be generated based on multiple light sources. That is, eacheyebox is generated based on output from a separate light source (e.g.,a separate set of one or more lasers).

While the above “multiple eyebox” approach enables small AR systems thatcan provide computer-generated perceptible information on curvedcombiners integrated with a lens for normal eyewear, knownimplementations of such an approach include several limitations to theirutility. For example, such solutions are limited to monochromatic imagesusing red lasers having different wavelengths (e.g., for dark,intermediate, and light red) because green or blue laser sources cannotbe manufactured small enough to fit within the relatively small formfactors needed to incorporate such AR systems into normal eyewear.Furthermore, the small form factor for the AR system limits the totalnumber of separate light sources that can be included in the system,thereby still limiting the overall eyebox size (e.g., the total size ofthe two or more eyeboxes) to a relatively small area.

FIG. 1 illustrates a prior AR system 100 that improves upon the MEMSscanner-based system described above. The AR system 100 of FIG. 1includes a projector 102 that projects light onto the surface of a HOE104 that, in turn, reflects the light towards an eye 106 a of user ofthe AR system 100. The HOE 104 includes an optical function that waspreviously recorded into the HOE 104. As used herein, an opticalfunction of a HOE defines the optical characteristics corresponding tohow light is reflected or transmitted through the HOE. Thus, the way inwhich the light from the projector 102 is reflected off the HOE 104 ofFIG. 1 is based on the optical function of the HOE 104. As describedmore fully below, the optical function of a HOE can be specificallydesigned and recorded into the HOE based on specific interferences oflight passing through an unprocessed HOE. Thus, the optical function ofa HOE may be designed independent of the shape of the HOE, which enablesHOEs with different optical functions to nevertheless have the sameshape corresponding to lenses of normal eyewear (or any other suitableshape).

As shown in FIG. 1, the projector 102 includes at least one light source108, a collimation lens 110, a MEMS scanner 112 (also referred to hereinas a scanning mirror), and a projection lens 114. The light source 108may include one or more of a vertical-cavity surface-emitting laser(VCSEL), an edge emitting laser, a micro light emitting diode (LED), aresonant cavity LED, a quantum dot laser, or any other suitable lightsource. The ability to use standard laser diodes enables the creationimages based on red, green, and blue lasers for full-color images. Thus,while the light source 108 is represented as a single unit, the lightsource 108 may include a plurality of light sources. For instance, thelight source 108 may include a red light source (e.g., a red laser), agreen light source (e.g., a green laser), and a blue light source (e.g.,a blue laser), also referred to herein as an RGB light source.

The collimation lens 110 collimates the light generated by the lightsource 108 and directs the collimated light towards the scanning mirror112. The scanning mirror 112 changes position (e.g., rotates on an axis)to reflect the collimated light at different angles, thereby redirectingthe light, via the projection lens 114, towards different areas on thesurface of the HOE 104. In some examples, the scanning mirror 112 movesrelative to two different axes to produce a two-dimensional projection.The projection lens 114 may correct optical aberrations such asastigmatism, coma, keystone, or the like. The collimation lens 110and/or the projection lens 114 may have an adjustable focal length toenable adjustments to the location of an overall eyebox 116 for the ARsystem 100.

As mentioned above, to enlarge the size of the overall eyebox 116, theoverall eyebox 116 is implemented by an array of multiple individualeyeboxes 118, 120, 122. As shown in FIG. 1, the separate individualeyeboxes 118, 120, 122 align with corresponding ones of multipledifferent sub-images 124, 126, 128, 130, 132 reflected off the HOE 104.In the illustrated example, each of the sub-images 124, 126, 128, 130,132 includes identical content. That is, the sub-images 124, 126, 128,130, 132 repeat from one sub-image to the next such that a userperceives the same information represented by the sub-images regardlessof the location of the user's eye within the overall eyebox 116.

Depending on eye position, the image perceived by users corresponds tothe content represented in one or more of the individual sub-images 124,126, 128, 130, 132. However, because the sub-images are the same, thelocation of the eye does not change the perceived content. Nevertheless,depending on the location of the eye 106 within the overall eyebox 116,the perceived image may be composed of the light from more than one ofthe sub-images 124, 126, 128, 130, 132. For example, the path ofreflected light corresponding to the second sub-image 126 is representedby the thick lines 134 shown in FIG. 1. Based on the particular opticalfunction recorded in the HOE 104, the HOE 104 causes the light toconverge to a focal point (i.e., the point where the two thick lines 134cross in FIG. 1). As shown in FIG. 1, the light associated with each ofthe sub-images 124, 126, 128, 130, 132 converges to a correspondingfocal point at a similar distance from the HOE 104 to define a focalplane 136 for the HOE 104. As the light associated with each sub-image124, 126, 128, 130, 132 continues past the focal plane 136, the lightdiverges until it overlaps with light from other sub-images (e.g.,within the individual eyeboxes 118, 120, 122). The overall eyebox 116 ispositioned at a distance from the HOE 104 where light from differentones of the sub-images 124, 126, 128, 130, 132 may be overlapping suchthat light from the different ones of the sub-images enters the pupil138 of the eye 106 at the same time for different positions of the eye106 within the eyebox 116. The portion of light from a particularsub-image received into the pupil 138 that contributes to the resultingimage perceived by the user depends upon the position of the eye 106within the overall eyebox 116. For example, as shown in FIG. 1, when theuser's pupil 138 is centered in the center eyebox 120, only a smallportion of the path of reflected light 134 associated with the secondsub-image 126 enters the user's pupil 138. As such, the light from thesecond-sub-image contributes only a small portion to the perceived imageviewed by users with their eye 106 in the position as shown in FIG. 1.If the eye 106 were to move to the left in the illustrated example(e.g., towards the left-most eyebox 118 of FIG. 1) a greater portion ofthe light associated with the second sub-image 126 would contribute tothe image perceived by the user.

Although light from more than one sub-image 124, 126, 128, 130, 132 mayenter the eye 106 of a user for any given position of the eye 106, theangle of such light as reflected from the HOE 104 is such that the lightfrom the different sub-images is combined to compose a consistent singleinstance of the content represented by any one of the sub-images 124,126, 128, 130, 132 as perceived by the user. That is, as a user movestheir eye 106 within the overall eyebox 116, the user will continuouslyperceive a complete representation of the content represented by thesub-images as if the user was viewing the entire content of only one ofthe sub-images 124, 126, 128, 130, 132. Light from multiple differentsub-images combine to compose a single representation of the content dueto the HOE 104 reflecting, based on the optical function, the light suchthat the chief rays (represented by the alternating dotted and dashedlines 140) of light associated with each sub-image are parallel to thechief rays 140 associated with the other sub-images. As used herein, theterm “chief ray” refers to the central ray of each sub-image 124, 126,128, 130, 132 reflected by the HOE 104. Thus, as shown in FIG. 1, thechief rays for the sub-images are neither converging nor diverging. Theparallel nature of the chief rays 140, as shown in FIG. 1, result in thechief rays converging (after passing through the lens of the eye 106) toa single point on the retina of the eye 106, thereby creating a singlepixel of a single image perceived by the user.

The field of view (FOV) for an AR system corresponds to the angularproportion of a full image that is visible to a user at a given point intime. As used herein, the “full image” refers to all of the lightprojected onto the HOE. Thus, the sum of the light from all of thesub-images 124, 126, 128, 130, 132 is the full image of the AR system100 of FIG. 1. The FOV for the AR system 100 of FIG. 1, from the viewpoint of the eye 106, is represented by the dashed line 142. As shown inFIG. 1, the FOV 142 corresponds to the area of the three centralsub-images 126, 128, 130 and excludes the outer two sub-images 124, 132.While the FOV 142 is less than the total image field of the full image,as described above, users nevertheless perceive the entire contentrepresented by the sub-images (referred to herein as the perceivedimage) because the perceived image at any given time (e.g., at anyposition of the eye in the eyebox) is limited to the content representedby a single sub-image. The multiple sub-images serve to enlarge theeyebox 116 so that the same perceived image may be viewed as the eye 106moves around within a larger area rather than being limited to a preciselocation.

The size of the FOV 142 is dependent on the focal length of the HOE 104with respect to each sub-image. The focal length of the HOE 104 isrelated to the distance between the HOE 104 and the focal plane 136. Asthe focal length (and corresponding distance to the focal plane 136) ofthe HOE 104 decreases, the FOV increases. However, decreasing the focallength in this manner results in a reduction in the resolution of theperceived image because the full image (corresponding to the combinationof all the sub-images) will take up a smaller area and because therewill be more diffraction. The size of the FOV 142 is also dependent onthe size of the individual sub-images 124, 126, 128, 130, 132. Inparticular, a larger FOV can be achieved by increasing size of thesub-images 124, 126, 128, 130, 132. Furthermore, larger sub-images alsoachieves higher resolution because, as described above, the perceivedimage at any discrete eye position within the eyebox 116 corresponds tothe content represented by a single one of the sub-images. Therefore,the resolution of the perceived image is tied to the resolution of asingle one of the sub-images. However, there are practical limits to howlarge each sub-image can be because increasing the sub-image size alsoincreases the distance between adjacent ones of the individual eyeboxes118, 120, 122. If the eye boxes are spaced apart by a distance that isgreater than the diameter of the pupil 138 of a user, the light fromdifferent ones of the sub-images would not be able to combine to form acomplete perceived image. Rather, the user would see only portions ofthe image at any one point in time with discontinuities or gaps betweenthe different portions as the user moved their eye around from oneindividual eyebox to the next.

Thus, while shorter focal lengths and larger sub-images result in alarger FOV, the shorter focal lengths lead to lower resolutions and thesize of the sub-images are limited to relatively small areas (defined bythe size of the pupil 138) also resulting in relative low resolutions.As such, a tradeoff between (1) a larger FOV or (2) a higher resolutionmust be made. In addition to limits on the size of the FOV relative tothe available resolution, the AR system 100 also presents certaininefficiencies. As mentioned above, depending on the location of auser's eye 106, a greater or lesser portion of the light from anyparticular sub-image 124, 126, 128, 130, 132 may enter the pupil 138with the remaining portion of light not being perceived by the user. Forsome sub-images, there may be a portion of associated light that willnever enter the eye 106. For example, as shown in FIG. 1, a portion 144of the light associated with the second sub-image 126 will never enterthe pupil 138 of the eye 106 (regardless of the eye's position) becauseit is angled away from the eye 106. An even greater portion of the lightassociated with the first sub-image 124 never reaches the user's eye106. The light that never hits the user's eye 106 can never be perceivedby the user and, thus, is wasted light that translates into unnecessaryconsumption of power and processing capacity to pulse the light source108 and direct the scanning mirror 112 to produce this light.

Examples disclosed herein overcome at least some of the limitations ofthe prior AR system 100 of FIG. 1 by achieving greater resolutionwithout being limited by an overly narrow FOV. Furthermore, examplesdisclosed herein achieve greater efficiency because more (e.g., all) ofthe light projected onto a HOE is reflected towards a user's eye so thatless light is wasted or lost by never hitting the eye. In some examples,no light is lost by directed all light toward an eyebox where the lightmay be perceived by users.

FIG. 2 illustrates an example AR system 200 that includes a projector202 and a HOE 204. In this example, the projector 202 of FIG. 2 issimilar or identical to the projector 102 of FIG. 1. However, thecontent represented by the full image (e.g., all the light) projectedfrom the projector 202 of FIG. 2 is different than the contentrepresented by the full image (e.g., all the light) projected from theprojector 102 of FIG. 1. In particular, as shown and described inconnection with FIG. 1, the full image projected from the projector 102corresponds to a plurality of sub-images 124, 126, 128, 130, 132, eachhaving the identical content. Only one instance of the content of thesub-images 124, 126, 128, 130, 132 is perceived by the user at a giventime such that the resolution of the AR system 100 of FIG. 1 is definedby the size of a single one of the sub-images 124, 126, 128, 130, 132.That is, the perceived image in FIG. 1 (corresponding to the content ofa single sub-image) is much smaller than the full image (correspondingto all the sub-images collectively). By contrast, the full imageprojected from the projector 202 of FIG. 2 corresponds to a singleunitary image 206 that may be perceived by a user. As such, theresolution of the AR system 200 of FIG. 2 is defined by the size of thefull image (e.g., the unitary image 206) with the possibility of everyportion of the full image containing different, non-repeating content.Of course, there is nothing preventing the unitary image 206 of FIG. 2from containing similar or repeating content within different regions ofthe image. However, such regions correspond to different parts of theentire content that may be perceived by a user rather than duplicateparts of the same content as is the case with the sub-images 124, 126,128, 130, 132 of FIG. 1. That is, the perceived image in FIG. 2 is thesame as the full image, both of which correspond to the unitary image206.

The HOE 204 of FIG. 2 includes a different optical function than the HOE104 of FIG. 1 such that the light from the projector 202 in FIG. 2 isreflected in a different manner than in FIG. 1. In particular, theoptical function recorded in the HOE 104 of FIG. 1 causes the light fromdiscrete portions of the full image (corresponding to the individualsub-images 124, 126, 128, 130, 132) to converge at a focal plane 136 andthen begin to diverge before reaching the eyebox 116 where the eye 106is located. By contrast, the optical function recorded in the HOE 204 ofFIG. 2 causes the full image (e.g., corresponding to the unitary image206) to converge towards a focal point 208 that is beyond an eyebox 210where the pupil 138 of the eye 106 is to be located. In the illustratedexample of FIG. 2, the focal point is located at the back of the user'seye 106 but may be positioned at different distances either inside theeye 106 or behind the back of the eye 106. Further, whereas the HOE 104of FIG. 1 reflects the projected light so that the chief rays 140associated with the sub-images 124, 126, 128, 130, 132 are parallel toone another, the HOE 204 of FIG. 4 causes the all the rays associatedwith the unitary image 206 to converge towards the focal point.

Causing the light to converge behind the user's pupil 138, as shown inFIG. 2, enables a larger individual eyebox 210 in which the unitaryimage 206 may be viewed as compared with the size of the individualeyeboxes 118, 120, 122 of FIG. 1. However, the arrangement shown in FIG.2 also decreases the FOV (represented by the dashed line 212) relativeto a total image field 214 corresponding to the full image of projectedlight (e.g., the unitary image 206 in this example). Furthermore, due tothe relatively small FOV 212 and relatively large size of the unitaryimage 206, only a portion of the unitary image 206 is viewable from theeyebox 210 at any given time. By moving their eye within the eyebox 210,users may view other portions of the unitary image 206 such that theentire image 206 is viewable, just not all at once. While the FOV 212 isrelatively small, using the unitary image 206 as the full imageprojected from the projector 202 as shown in FIG. 2 enables a muchlarger resolution for the perceived image. Thus, FIG. 2 represents atrade off between the FOV 212 and resolution in favor of higherresolution.

FIG. 3 illustrates an example AR system 300 constructed in accordancewith teachings of this disclosure. The system 300 of FIG. 3 takesadvantage of the higher resolution image described in connection withFIG. 2 and the larger FOV described in connection with FIG. 1. Theexample AR system 300 includes a projector 302 and a HOE 304. In thisexample, the projector 302 of FIG. 3 is similar or identical to theprojector 102 of FIG. 1. However, the content represented by the fullimage (e.g., all the light) projected from the projector 302 of FIG. 3is different than the content represented by the full image (e.g., allthe light) projected from the projector 102 of FIG. 1. As with FIG. 1,the full image projected from the projector 302 of FIG. 3 corresponds toa plurality of sub-images 306, 308, 310, 312, 314. However, unlike thesub-images 124, 126, 128, 130, 132 of FIG. 1, the sub-images 306, 308,310, 312, 314 of FIG. 3 are not identical to each other, but instead,each contains at least some non-repeating content with respect to otherones of the sub-images 306, 308, 310, 312, 314. Further, as explainedbelow, adjacent ones of the sub-images 306, 308, 310, 312, 314 includesome repeating or common content. That is, a first portion of ones ofthe sub-images may have overlapping content relative to other sub-imageswith a second portion that is non-overlapping content relative to theother sub-images. Further detail regarding the interrelationship of thecontent in the different sub-images 306, 308, 310, 312, 314 of FIG. 3 isdescribed below in connection with FIG. 4.

The HOE 304 of FIG. 3 includes a different optical function than theHOEs 104, 204 of FIGS. 1 and/or 2. As represented in the illustratedexample of FIG. 3, the optical function recorded in the HOE 304 causesthe light associated with each respective sub-image 306, 308, 310, 312,314 to converge at a focal plane 316 and then begin to diverge beforereaching an eyebox 318 where a user's eye 106 is located. The distancebetween the focal plane 316 and the HOE 304 in FIG. 3 is greater thanthe distance between the focal plane 136 and the HOE 104 of FIG. 1. Asdescribed above, these distances correspond to the focal length of therespective HOEs 104, 304 with larger focal lengths resulting in asmaller FOV but providing a higher resolution. Thus, the example ARsystem 300 of FIG. 3 provides greater resolution than the AR system 100of FIG. 1.

The reduction in the FOV of the HOE 304 of FIG. 3 caused by the greaterfocal length is offset by the optical function of the HOE 304 causingthe chief rays 320 associated with the sub-images 306, 308, 310, 312,314 (i.e., the central rays of the separate sub-images) to convergetowards a focal point 322 beyond the eyebox 318 behind the pupil 138 ofthe eye 106. In the illustrated example of FIG. 3, the focal point 322is located at the back of the user's eye 106 but may be positioned atdifferent distances either inside the eye 106 or behind the back of theeye 106. In other examples, the chief rays 320 may converge at the pupil138 of the eye 106. In other examples, the chief rays 320 may convergeat a point in front of the pupil 138. As represented in the illustratedexamples, causing the chief rays 320 of light for the separatesub-images 306, 308, 310, 312, 314 to converge behind the pupil 138, asshown in FIG. 3, enables a larger FOV (represented by the dashed line324) for the AR system 300 of FIG. 3 than the FOV 212 of the AR system200 of FIG. 2. That is, the FOV 324 of FIG. 3 corresponds to a muchlarger proportion of the total image field 326 than the FOV 212 of FIG.2 relative to the corresponding total image field 214. As a result,increases in resolution from a longer focal length are achieved withoutbeing limited by an overly narrow FOV.

In addition to an increased optical resolution achieved by the longerfocal length, the arrangement shown in FIG. 3 also enables a higherresolution for the perceived image than in FIG. 1 based on the way inwhich the separate sub-images 306, 308, 310, 312, 314 in FIG. 3 arecombined to contribute to the perceived image viewed from the eyebox318. As described above, the resolution for the perceived imagegenerated by the AR system 100 of FIG. 1 corresponds to the size of asingle one of the sub-images 124, 126, 128, 130, 132 because each of theseparate sub-images 124, 126, 128, 130, 132 independently repeats thesame content that makes up the perceived image. By contrast, theresolution for the perceived image generated by the AR system 300 ofFIG. 3 corresponds to the size of the non-repeating content across allof the sub-images 306, 308, 310, 312, 314, which is greater than thesize of a single sub-image. Put another way, the resolution for theperceived image generated by the AR system 300 of FIG. 3 corresponds tothe size of a first one of the sub-images 306, 308, 310, 312, 314 plusthe size of non-duplicative content represented in other ones of thesub-images 306, 308, 310, 312, 314 that is not common with the contentin the first sub-image. This is illustrated more clearly in FIG. 4.

FIG. 4 illustrates an example AR system 400 constructed similar to theAR system 300 of FIG. 3. That is, the example AR system 400 of FIG. 4includes a projector 402 similar or identical to the projector 302 ofFIG. 3 and a HOE 404 that reflects the light from the projector with thechief rays for the different sub-images converging to a focal pointbeyond an eyebox for the HOE 404. FIG. 4 differs from FIG. 3 in thatlight projected from the projector 402 and reflected by the HOE 404includes seven sub-images 406, 408, 410, 412, 414, 416, 418 instead offive shown in FIG. 3. In the illustrated example of FIG. 4, the contentof the different sub-images 406, 408, 410, 412, 414, 416, 418 arerepresented as corresponding to different portions of a perceived image420 including the moon, a cloud, and the sun. The perceived image 420shown in the illustrated example includes eleven labelled pixels P0-P10corresponding to the boundaries of different ones of the sevensub-images 406, 408, 410, 412, 414, 416, 418. For example, the firstsub-image 406 corresponds to the left-most portion of the perceivedimage 420 extending between pixels P0 and P4, the second sub-image 406corresponds to a shifted portion of the perceived image 420 extendingfrom pixels P1 to P5, the third sub-image 408 corresponds to the portionof the perceived image 420 extending from pixels P2 to P6, the fourthsub-image 410 corresponds to the portion of the perceived image 420extending from pixels P3 to P7, the fifth sub-image 412 corresponds tothe portion of the perceived image 420 extending from pixels P4 to P8,the sixth sub-image 414 corresponds to the portion of the perceivedimage 420 extending from pixels P5 to P9, and the seventh sub-image 418corresponds to the portion of the perceived image 420 extending frompixels P6 to P10. In some examples, the width and spacing (e.g., amountof overlap) of the sub-images 406, 408, 410, 412, 414, 416, 418corresponding to successively shifted portions of the perceived image420 may be consistent across the total width of the perceived image. Inother examples, the width and/or the spacing of ones of the sub-imagesmay be different than the width and/or spacing of different ones of thesub-images. Furthermore, there may be more or fewer sub-images used toform the total perceived image 420 than shown in FIG. 5. Further, whileall of the sub-images 406, 408, 410, 412, 414, 416, 418 are shownarranged in a horizontal line, in some examples, the sub-images may bespaced vertically and/or spaced in both the horizontal and verticaldirections to form a two-dimensional array of sub-images.

For the sake of clarity, only the second, third, fourth, and fifthsub-images 408, 410, 412, 414 are mapped to the perceived image 420 inFIG. 4 and to the HOE 404. Further, only the light rays associated withthese four sub-images 408, 410, 412, 414 are represented as beingreflected off the HOE 404 in FIG. 4. However, it should be understoodthat the projector 402 projects light corresponding to all sevensub-images 406, 408, 410, 412, 414, 416, 418, which is then reflected bythe HOE 404 towards the user's eye 106. Thus, as described above, thecombination of all the sub-images 406, 408, 410, 412, 414, 416, 418corresponds to the full image projected by the projector 402. As isapparent from the illustrated example, the perceived image 420 (e.g.,the content perceived by a user) is different than the full image (e.g.,all the light) projected from the projector 402 because there is overlapin the content represented in adjacent ones of the sub-images 406, 408,410, 412, 414, 416, 418. As explained above in connection with FIG. 1,light associated with different ones of the sub-images 406, 408, 410,412, 414, 416, 418 may combine to compose the image as perceived by theuser (e.g., the perceived image 420). For instance, as shown in theillustrated example, all of the light rays from the fourth sub-image 412enter the pupil 138 of the eye 106; only some of the light raysassociated with the third and fifth sub-images 410, 414 enter the pupil138; and none of the light rays associated with the second sub-image 408enter the pupil 138. Although not represented, none of the light raysfrom any of the other sub-images 406, 416, 418 enter the eye 106.

In the illustrated example of FIG. 4, the shaded portions of the lightrays, the sub-images 406, 408, 410, 412, 414, 416, 418, and theperceived image 420 represent what the user perceives based on thecurrent eye position. The non-shaded portions are indicative of contentthat cannot be perceived by the user based on the current eye position.That is, as with the AR system 200 of FIG. 2, users perceive less thanall the content represented in the perceived image 420 for any givenposition of their eye within the eyebox but may perceive the entireimage by moving their eye around.

The light shaded portions 422 correspond to content that is repeatedbetween the different sub-images contributing to the current view (e.g.,what the eye perceives if stationary) of the perceived image 420 (e.g.,the third, fourth and fifth sub-images 410, 412, 414 in the illustratedexample). Thus, as shown in the illustrated example, all of the contentrepresented in the fourth sub-image 412 corresponds to contentrepresented in either the third or fifth sub-images 410, 414. Althoughall of the content of the fourth sub-image 412 is repeated in portionsof the third and fifth sub-images 410, 414, there are neverthelessportions of the content in the fourth sub-image 412 that uniquelycontribute to the image perceived by the eye 106 because the lightassociated with the matching content in the other sub-images does notenter the pupil of the eye 106. That is, the fourth sub-image 412 is theonly sub-image that contributes light corresponding to the contentextending between pixels P4 and P6 in the perceived image 420 as viewedby the eye 106 shown in the illustrated example.

The dark shaded portions 424 correspond to non-repeating content amongthe different sub-images contributing to the user's view of theperceived image 420. In contrast with the fourth sub-image 412, portionsof the third and fifth sub-images 410, 414 are unique relative to theother two sub-images contributing to the current view of the eye 106.That is, a portion of the third sub-image 410 includes content that isnot included in either of the fourth or fifth sub-images 412, 414. Forexample, the light corresponding to the content between pixels P2 and P3from the third sub-image 410 is content not included in the fourth orfifth sub-images 412, 414. As such, the content between pixels P2 and P3is exclusively contributed to the user's perception of the image fromthe third sub-image 410. A similar situation applies in relation to thefifth sub-image 414 and the content between pixels P7 and P8. Of course,the content between pixels P2 and P3 and between pixels P7 and P8 isrepeated in other ones of the sub-images, but these sub-images do notcontribute to the portion of the perceived image 420 viewed by the eye106 as shown in FIG. 1. In the illustrated example, at least some of thesub-images may have non-repeating content that is unique relative to allother sub-images. In particular, in the illustrated example of FIG. 4,the content between pixels P0 and P1 is only provided in the firstsub-image 406. Likewise, the content between pixels P9 and P10 is onlyprovided in the seventh sub-image 418.

FIG. 5 illustrates the perceived image 420 of FIG. 4 with dark lines torepresent the FOV 502 of the perceived image 420 relative to the totalimage field 504 of the perceived image 420. While users cannot see theentire image 420 at a single instance in time, the FOV 502 enables usersto view a much larger proportion of the perceived image 420 at a singletime than would be possible using the AR system 200 of FIG. 2. Thelarger FOV 502 in FIG. 5 comes at some cost to the resolution of theperceived image 420 relative to the example AR system 200 of FIG. 2.However, as mentioned above, the resolution of the perceived image 420in FIG. 5 is still greater than the resolution of the perceived imageproduced by the AR system 100 of FIG. 1. More specifically, returning toFIG. 4, the resolution of the perceived image 420 corresponds to thetotal size of the non-repeating content associated with the perceivedimage. For example, the first and fifth sub-images 406, 414 correspondto directly adjacent but non-overlapping portions of the perceived image420. Specifically, the first sub-image 406 includes the contentextending between pixels P0 and P4 and the fifth sub-image 414 includesthe content extending between pixels P4 and P8. Additionally,approximately one half of the seventh sub-image 418 includes content(e.g., between pixels P8 and P10) that is non-repeating with the contentin the first and fifth sub-images 406, 414. Accordingly, the resolutionof the perceived image 420 corresponds to approximately the size of twoand half of the sub-images. This is a significant improvement over theAR system 100 of FIG. 1, which has a resolution corresponding to asingle one of the sub-images.

The particular resolution and the particular FOV for an AR system may betailored to particular applications in accordance with teachingsdisclosed herein by selecting the number of sub-images, sub-image sizes,and focal length of the HOE along a continuum between the AR system 100of FIG. 1 and the AR system 200 of FIG. 2. As described above, the ARsystem 100 of FIG. 1 has a relatively low resolution that corresponds tothe size of an individual sub-image but a relatively large FOV thatenables users to view the entire perceived image at a single point intime (e.g., without having to move the eye around). At the other end ofthe spectrum, the example AR system 200 of FIG. 2 provides relativelyhigh resolution because there is only a single unitary image 206.However, the FOV of the AR system 200 is relatively small such that onlya small portion of the perceived image (e.g., the unitary image 206) isvisible at one time. Examples disclosed herein enable the design andconstruction of AR systems that strike suitable balances between thesetwo extremes to achieve relatively wide FOVs while also providingrelatively high resolutions.

FIG. 6 illustrates an example system 600 to record an optical functioninto the HOE 602 that may be used to implement the example AR systems200, 300, 400 of FIGS. 2-4. For purposes of illustration, the HOE 602 isshown to be flat, but may be curved in the same manner as the HOEs 204304, 404 of FIGS. 2-4. In some examples, the HOE 602 corresponds to areflective volume hologram. An advantage of recording an opticalfunction into a reflective volume hologram is that the HOE 602 can beany desired shape and/or have any suitable physical structure. Asdescribed above, in some examples, the HOE 602 is curved to correspondto the curvature of normal eye glasses.

In the illustrated example, the HOE 602 is positioned a distance from amicrolens array 604. As shown in the illustrated example, the lens array604 includes a series of lenses. The number of lenses in the lens array604 corresponds to the number of sub-images intended to be reflected bythe HOE 602. Thus, to record the optical function associated with theHOE 204 of FIG. 2, the lens array 604 may be replaced by a single lensbecause the HOE 204 is intended to reflect a single unitary image ratherthan multiple sub-images.

The example system 600 also includes decollimation lens 606 that ispositioned in alignment with the lens array 604 and the HOE 602 as shownin FIG. 6. In the illustrated example, the decollimation lens 606 is adiverging lens. To record an optical function in the HOE 602, a firstlight source 608 generates a first beam of light 610 directed towardsthe diverging lens 606. In some examples, the first beam of light 610 isa collimated beam of light such that all light rays in the beam are inparallel. As the first beam of light 610 passes through the diverginglens 606, the light rays diverge outward from a focal point 612 definedby a focal length 614 of the diverging lens 606. In some examples, thefocal length 614 defines the location of the focal points 208, 322 atwhich the chief rays of the light reflected off the HOE is to converge.After the rays of the first beam of light 610 pass through the diverginglens 606, the rays next pass through the lens array 604 towards the HOE602. The lens array 604 refocuses the light and causes discrete portionsof the rays to converge at different points on a focal plane 616 beforediverging and then hitting the HOE 602. In some examples, thedimensions, shapes, and/or focal lengths of the individual lenses inlens array 604 may differ from one another. The lenses in the lens array604 may have different sizes, different shapes, be aspherical,achromatic, diffractive, etc.

At the same time that the first beam of light 610 is being directedtowards the HOE 602 as described above, a second light source 618generates a second beam of light 620. In some examples, the second beamof light 620 and the first beam of light 610 are directed towardopposite sides of HOE 602. As shown in the illustrated example, thesecond beam of light 620 converges towards a second focal point 622. Insome examples, the location of the second focal point 622 relative tothe HOE 602 corresponds to the position of the scanning mirror 112implemented in the projectors 202, 302, 402 of FIGS. 2-4.

The HOE 602 is a photopolymer that reacts to light. In some examples,the HOE 602 is transparent to allow light to pass therethrough. Thetransparent nature of the HOE 602 enables the HOE 602 to be implementedin AR devices that allow users to view the real-world (through the HOE602) while also viewing computer-generated perceptual informationoverlaid on the real-world view (reflected off the HOE 602). In otherexamples, the HOE 602 may be implemented in virtual reality devices. Insome such examples, the HOE 602 may not be transparent. The opticalfunction for the HOE 602 is recorded in the HOE by the interference ofthe first and second beams of light 610, 620 passing through the HOE.Once the optical function is recorded into the HOE 602 in this manner,light projected onto the HOE from the second focal point 622 (i.e., inthe opposite direction to the second beam of light 620) will bereflected off the HOE to follow the reverse path of the first beam oflight 610 produced by passing through the diverging lens 606 and lensarray 604. Of course, during implementation, the diverging lens 606 andlens array 604 will no longer be present such that the path of reflectedlight will correspond to the paths of light as shown in FIGS. 2-4.

FIG. 7 illustrates another example system 700 to record an opticalfunction into the HOE 702 that may be used to implement the example ARsystems 200, 300, 400 of FIGS. 2-4. For purposes of illustration, theHOE 702 is shown to be flat, but may be curved in the same manner as theHOEs 204 304, 404 of FIGS. 2-4. The HOE 702 of FIG. 7 may be the similaror identical to the HOE 602 of FIG. 6. In the illustrated example ofFIG. 7, the system 700 includes a microlens array 704 positioned betweenthe HOE 702 and a decollimation lens 706. Unlike the decollimation lens606 of FIG. 6, the decollimation lens 706 of the example system 700 ofFIG. 7 is a converging lens.

To record an optical function in the HOE 702, a first light source 708generates a first beam of light 710 directed towards the converging lens706. In some examples, the first beam of light 710 is a collimated beamof light such that all light rays in the beam are in parallel. As thefirst beam of light 710 passes through the converging lens 706, thelight rays converge toward a focal point 712 defined by a focal length714 of the converging lens 706. In some examples, the focal length 714defines the location of the focal points 208, 322 at which the chiefrays of the light reflected off the HOE is to converge. After the raysof the first beam of light 710 pass through the converging lens 706, therays next pass through the lens array 704 towards the HOE 702. The lensarray 704 refocuses the light and causes discrete portions of the raysto converge toward different points on a focal plane 716 as the lighthits the HOE 702 as shown in the illustrated example. In some examples,the dimensions, shapes, and/or focal lengths of the individual lenses inlens array 704 may differ from one another. The lenses in the lens array704 may have different sizes, different shapes, be aspherical,achromatic, diffractive, etc.

At the same time that the first beam of light 710 is being directedtowards the HOE 702 as described above, a second light source 718generates a second beam of light 720. In some examples, the second beamof light 720 and the first beam of light 710 are directed towardopposite sides of HOE 702. As shown in the illustrated example, thesecond beam of light 720 diverges outwards from a second focal point722. In some examples, the location of the second focal point 722relative to the HOE 702 corresponds to the position of the scanningmirror 112 implemented in the projectors 202, 302, 402 of FIGS. 2-4.That is, the second light source 718 is positioned at the same locationas the scanning mirror 112.

As described above with respect to FIG. 6, the HOE 702 is a photopolymerthat reacts to light. As a result, the optical function for the HOE 702is recorded in the HOE by the interference of the first and second beamsof light 710, 720 passing through the HOE. Once the optical function isrecorded into the HOE 702 in this manner, light projected onto the HOEfrom the second focal point 722 (i.e., in the direction of the secondbeam of light 720) will be reflected off the HOE to follow the path ofthe first beam of light 710 produced by passing through the converginglens 706 and lens array 704.

FIG. 8 illustrates an example AR device 800 constructed in accordancewith teachings disclosed herein. The example AR device 800 includes aframe 802 to hold one or more eyepiece lenses 804 that include a HOE 806with an optical function recorded thereon. While the frame 802 is shownas a pair of eye glasses, the frame may correspond to any suitablewearable AR device. In some examples, the HOE 806 is constructed similarto the HOEs 204, 304, 404 of FIGS. 2-4. The HOE 806 may be integratedwith the eyepiece lens 804 or manufactured separately therefrom andaffixed to a surface of the eyepiece lens 804. In some examples, aseparate HOE 806 is associated with each eyepiece lens 804. In theillustrated example, a projector 808 is positioned within the frame 802at a location providing a direct line of sight with the HOE 806 toproject light toward the HOE 806 through free space. In some examples,the projector 808 may be similar or identical to any of the projectors102, 202, 302, 402 of FIGS. 1-4.

In some examples, the AR device 800 includes one or more image sensors810 (e.g., a camera) to capture images of an environment surrounding theAR device 800. The example AR device 800 may also include one or moreother sensors 812 to determine a position and/or orientation of the ARdevice 800 relative to the surrounding environment. The other sensors812 may include motion sensors (e.g., accelerometers, gyroscopes, etc.),location sensors (e.g., a global positioning system, magnetometers,etc.), depth sensors, etc.

In the illustrated example, the AR device 800 includes an example ARcontrol system 814. The projector 808, the image sensor 810, the othersensors 812, and/or the AR control system 814 may be powered by a powersource 816. In some examples, the power source 816 is a battery or otherpower supply incorporated into in the frame 802 of the AR device 800. Inother examples, the power source 816 may be a physical interface used toconnect an external power supply.

As shown in the illustrated example, the AR control system 814 includesan example surroundings analyzer 818, an example AR image generator 820,an example projection controller 822, and an example communicationsinterface 824. The example surroundings analyzer 818 analyzes imagescaptured by the image sensor 810 and/or feedback from the other sensors812 to identify objects and/or circumstances in a surroundingenvironment and determine the positional relationship of the AR device800 relative to such objects and/or circumstances. The example AR imagegenerator 820 generates an AR image to be projected onto the HOE 806 toenhance or augment a user's view of the surrounding environment throughthe eyepiece lenses 804. The example projection controller 822 controlsthe operation of the projector 808 based on the AR image generated bythe AR image generator 820. For example, the projection controller 822controls when the light source 108 projects light and/or the particularcolor of light (if, for example, the light source 108 includes differentcolors of light sources). Further, the projection controller 822controls the movement of the scanning mirror 112 to direct the lightproduced by the light source 108 to the correct location on the HOE 806.The example communications interface 824 enables communications betweenthe AR control system 814 and the other components on the AR device 800.In some examples, one or more of the surroundings analyzer 818, the ARimage generator 820, and/or the projection controller 822 areimplemented on a separate device external to the AR device 800 In suchexamples, the communications interface 824 enables communicationsbetween the external device and the components on the AR device 800.

While an example manner of implementing the AR control system 814 ofFIG. 8 is illustrated in FIG. 8, one or more of the elements, processesand/or devices illustrated in FIG. 4 may be combined, divided,re-arranged, omitted, eliminated and/or implemented in any other way.Further, the example surroundings analyzer 818, the example AR imagegenerator 820, the example projection controller 822, the examplecommunications interface 824 and/or, more generally, the example ARcontrol system 814 of FIG. 8 may be implemented by hardware, software,firmware and/or any combination of hardware, software and/or firmware.Thus, for example, any of the example surroundings analyzer 818, theexample AR image generator 820, the example projection controller 822,the example communications interface 824 and/or, more generally, theexample AR control system 814 could be implemented by one or more analogor digital circuit(s), logic circuits, programmable processor(s),programmable controller(s), graphics processing unit(s) (GPU(s)),digital signal processor(s) (DSP(s)), application specific integratedcircuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or fieldprogrammable logic device(s) (FPLD(s)). When reading any of theapparatus or system claims of this patent to cover a purely softwareand/or firmware implementation, at least one of the example surroundingsanalyzer 818, the example AR image generator 820, the example projectioncontroller 822, and/or the example communications interface 824 is/arehereby expressly defined to include a non-transitory computer readablestorage device or storage disk such as a memory, a digital versatiledisk (DVD), a compact disk (CD), a Blu-ray disk, etc. including thesoftware and/or firmware. Further still, the example AR control system814 of FIG. 8 may include one or more elements, processes and/or devicesin addition to, or instead of, those illustrated in FIG. 8, and/or mayinclude more than one of any or all of the illustrated elements,processes and devices. As used herein, the phrase “in communication,”including variations thereof, encompasses direct communication and/orindirect communication through one or more intermediary components, anddoes not require direct physical (e.g., wired) communication and/orconstant communication, but rather additionally includes selectivecommunication at periodic intervals, scheduled intervals, aperiodicintervals, and/or one-time events.

A flowchart representative of example hardware logic, machine readableinstructions, hardware implemented state machines, and/or anycombination thereof for implementing the AR device 800 of FIG. 8 isshown in FIG. 9. The machine readable instructions may be an executableprogram or portion of an executable program for execution by a computerprocessor such as the processor 1112 shown in the example processorplatform 1100 discussed below in connection with FIG. 11. The programmay be embodied in software stored on a non-transitory computer readablestorage medium such as a CD-ROM, a floppy disk, a hard drive, a DVD, aBlu-ray disk, or a memory associated with the processor 1112, but theentire program and/or parts thereof could alternatively be executed by adevice other than the processor 1112 and/or embodied in firmware ordedicated hardware. Further, although the example program is describedwith reference to the flowchart illustrated in FIG. 9, many othermethods of implementing the example AR device 800 may alternatively beused. For example, the order of execution of the blocks may be changed,and/or some of the blocks described may be changed, eliminated, orcombined. Additionally or alternatively, any or all of the blocks may beimplemented by one or more hardware circuits (e.g., discrete and/orintegrated analog and/or digital circuitry, an FPGA, an ASIC, acomparator, an operational-amplifier (op-amp), a logic circuit, etc.)structured to perform the corresponding operation without executingsoftware or firmware.

As mentioned above, the example process of FIG. 9 may be implementedusing executable instructions (e.g., computer and/or machine readableinstructions) stored on a non-transitory computer and/or machinereadable medium such as a hard disk drive, a flash memory, a read-onlymemory, a compact disk, a digital versatile disk, a cache, arandom-access memory and/or any other storage device or storage disk inwhich information is stored for any duration (e.g., for extended timeperiods, permanently, for brief instances, for temporarily buffering,and/or for caching of the information). As used herein, the termnon-transitory computer readable medium is expressly defined to includeany type of computer readable storage device and/or storage disk and toexclude propagating signals and to exclude transmission media.

“Including” and “comprising” (and all forms and tenses thereof) are usedherein to be open ended terms. Thus, whenever a claim employs any formof “include” or “comprise” (e.g., comprises, includes, comprising,including, having, etc.) as a preamble or within a claim recitation ofany kind, it is to be understood that additional elements, terms, etc.may be present without falling outside the scope of the correspondingclaim or recitation. As used herein, when the phrase “at least” is usedas the transition term in, for example, a preamble of a claim, it isopen-ended in the same manner as the term “comprising” and “including”are open ended. The term “and/or” when used, for example, in a form suchas A, B, and/or C refers to any combination or subset of A, B, C such as(1) A alone, (2) B alone, (3) C alone, (4) A with B, (5) A with C, (6) Bwith C, and (7) A with B and with C.

The process of FIG. 9 begins at block 902 where the example AR imagegenerator 820 generates an AR image (e.g., the perceived image 420 ofFIG. 4). At block 904, the example projector 808 projects light based onthe AR image toward the HOE 806 having a recorded optical function. TheHOE 806 reflects the light based on the optical function to cause chiefrays of a reflected image to converge at a focal point beyond an eyeboxassociated with the HOE 806. At block 906, the example projectioncontroller 822 determines whether there is more light to project. If so,control returns to block 902. Otherwise, the example process of FIG. 9ends.

FIG. 10 is a flowchart representative of an example process to record anoptical function in an unprocessed HOE to manufacture the HOEs 204, 304,404, 806 of FIGS. 2-4 and/or 8. The example process begins at block 1002by positioning a lens array 604, 704 between a decollimation lens (e.g.,the diverging lens 606 or the converging lens 706) and a HOE 602, 702.At block 1004, the process includes transmitting a first beam ofcollimated light 610, 710 through the decollimation lens 606, 706 andthe lens array 604, 704 toward a first side of the HOE 602, 702. Atblock 1006, the process includes transmitting a second beam of light620, 720 toward a second side of the HOE 602 to cause interferencesbetween the first and second beams of light 610, 620. Thereafter, theexample process of FIG. 10 ends.

FIG. 11 is a block diagram of an example processor platform 1100structured to execute the instructions of FIG. 9 to implement the ARdevice 800 of FIG. 8. The processor platform 1100 can be, for example, aserver, a personal computer, a workstation, a self-learning machine(e.g., a neural network), a mobile device (e.g., a cell phone, a smartphone, a tablet such as an iPad™), a personal digital assistant (PDA), aheadset or other wearable device, or any other type of computing device.

The processor platform 1100 of the illustrated example includes aprocessor 1112. The processor 1112 of the illustrated example ishardware. For example, the processor 1112 can be implemented by one ormore integrated circuits, logic circuits, microprocessors, GPUs, DSPs,or controllers from any desired family or manufacturer. The hardwareprocessor may be a semiconductor based (e.g., silicon based) device. Inthis example, the processor implements the example surroundings analyzer818, the example AR image generator 820, and the example projectioncontroller 822.

The processor 1112 of the illustrated example includes a local memory1113 (e.g., a cache). The processor 1112 of the illustrated example isin communication with a main memory including a volatile memory 1114 anda non-volatile memory 1116 via a bus 1118. The volatile memory 1114 maybe implemented by Synchronous Dynamic Random Access Memory (SDRAM),Dynamic Random Access Memory (DRAM), RAMBUS® Dynamic Random AccessMemory (RDRAM®) and/or any other type of random access memory device.The non-volatile memory 1116 may be implemented by flash memory and/orany other desired type of memory device. Access to the main memory 1114,1116 is controlled by a memory controller.

The processor platform 1100 of the illustrated example also includes aninterface circuit 1120. The interface circuit 1120 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), a Bluetooth® interface, a near fieldcommunication (NFC) interface, and/or a PCI express interface. In thisexample, the interface circuit 1120 implements the examplecommunications interface 824.

In the illustrated example, one or more input devices 1122 are connectedto the interface circuit 1120. The input device(s) 1122 permit(s) a userto enter data and/or commands into the processor 1112. The inputdevice(s) can be implemented by, for example, an audio sensor, amicrophone, a camera (still or video), a keyboard, a button, a mouse, atouchscreen, a track-pad, a trackball, isopoint and/or a voicerecognition system.

One or more output devices 1124 are also connected to the interfacecircuit 1120 of the illustrated example. The output devices 1124 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay (LCD), a cathode ray tube display (CRT), an in-place switching(IPS) display, a touchscreen, etc.), a tactile output device, a printerand/or speaker. The interface circuit 1120 of the illustrated example,thus, typically includes a graphics driver card, a graphics driver chipand/or a graphics driver processor.

The interface circuit 1120 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem, a residential gateway, a wireless access point, and/or a networkinterface to facilitate exchange of data with external machines (e.g.,computing devices of any kind) via a network 1126. The communication canbe via, for example, an Ethernet connection, a digital subscriber line(DSL) connection, a telephone line connection, a coaxial cable system, asatellite system, a line-of-site wireless system, a cellular telephonesystem, etc.

The processor platform 1100 of the illustrated example also includes oneor more mass storage devices 1128 for storing software and/or data.Examples of such mass storage devices 1128 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, redundantarray of independent disks (RAID) systems, and digital versatile disk(DVD) drives.

The machine executable instructions 1132 of FIG. 9 may be stored in themass storage device 1128, in the volatile memory 1114, in thenon-volatile memory 1116, and/or on a removable non-transitory computerreadable storage medium such as a CD or DVD.

From the foregoing, it will be appreciated that example methods,apparatus and articles of manufacture have been disclosed that enableHOEs that enables AR images with higher resolutions and/or larger FOVsthan previously known solutions based on components capable of beingconcealed and/or otherwise incorporated into the frames of normaleyewear. This is made possible by recording optical functions in suchHOEs that cause the chief rays of one or more images from a projector toconverge at a focal point beyond an eyebox for the HOE (corresponding tothe location of a pupil when a user is viewing the image(s)). The raysconverging beyond the eyebox enable a large eyebox and higherresolution. Further, the use of multiple sub-images with portionscontaining non-repeating content enables larger FOVs.

Example 1 includes an augmented reality (AR) device comprising aholographic optical element (HOE) including a recorded optical function,and a projector to emit light toward the HOE, the HOE to reflect thelight based on the optical function to produce a full imagecorresponding to content perceivable by a user viewing the reflectedlight from within an eyebox, a first portion of the content viewablefrom a first location within the eyebox, a second portion of the contentviewable from a second location within the eyebox, the first portionincluding different content than the second portion that isnon-repeating between the first and second portions.

Example 2 includes the AR device as defined in example 1, wherein thefull image is composed of portions of the light associated withdifferent ones of a plurality of sub-images, the HOE to reflect thelight based on the optical function so that chief light rays for theplurality of sub-images converge to a focal point, the eyebox locatedbetween the focal point and the HOE.

Example 3 includes the AR device as defined in example 2, wherein afirst sub-image of the plurality of sub-images includes the firstportion of the content of the full image and a second sub-image of theplurality of sub-images includes the second portion of the content.

Example 4 includes the AR device as defined in example 3, wherein thefirst sub-image and the second sub-image include a same portion of thefull image.

Example 5 includes the AR device as defined in any one of examples 1-4,wherein the HOE is transparent.

Example 6 includes the AR device as defined in any one of examples 1-5,wherein the HOE is a reflective volume hologram.

Example 7 includes the AR device as defined in any one of examples 1-6,wherein the HOE is curved.

Example 8 includes the AR device as defined in any one of examples 1-7,wherein the projector includes a red light source, a green light source,and a blue light source.

Example 9 includes the AR device as defined in any one of examples 1-8,wherein the light is projected through free space between the projectorand the HOE.

Example 10 includes the AR device as defined in example 1, furtherincluding a frame wearable by the user, the frame to support theprojector, and an eyepiece lens within the frame, the HOE positioned onthe eyepiece lens.

Example 11 includes an augmented reality (AR) device comprising aprojector to project light associated with first and second sub-images,and a holographic optical element (HOE) including an optical functionrecorded therein, the HOE to reflect the first and second sub-imagestoward an eyebox based on the optical function, the first sub-imageincluding first content corresponding to a first portion of a full imageperceivable by a user from the eyebox, the second sub-image includingsecond content corresponding to a second portion of the full image, thefirst sub-image not including the second content.

Example 12 includes the AR device as defined in example 11, wherein thefull image is composed of portions of the light associated with thefirst and second sub-images.

Example 13 includes the AR device as defined in any one of examples 11or 12, wherein the HOE is to reflect the light based on the opticalfunction so that chief light rays for the first and second sub-imagesconverge to a point behind a pupil of the user viewing the full imagefrom the eyebox.

Example 14 includes the AR device as defined in any one of examples11-13, wherein both the first and second sub-image include third contentcorresponding to a third portion of the full image.

Example 15 includes the AR device as defined in any one of examples11-14, wherein the HOE is transparent.

Example 16 includes the AR device as defined in any one of examples11-15, wherein the HOE is a reflective volume hologram.

Example 17 includes the AR device as defined in any one of examples11-16, wherein the HOE is curved.

Example 18 includes the AR device as defined in any one of examples11-17, wherein the projector includes a red light source, a green lightsource, and a blue light source.

Example 19 includes the AR device as defined in any one of examples11-18, wherein the light is projected through free space between theprojector and the HOE.

Example 20 includes the AR device as defined in any one of examples11-19, further including a frame wearable by the user, the frame tosupport the projector, and an eyepiece lens within the frame, the HOEincorporated into the eyepiece lens.

Example 21 includes a system comprising a holographic optical element(HOE), a first light source to direct a first beam of light toward theHOE from a first direction, the first beam of light being collimated, asecond light source to direct a second beam of light toward the HOE froma second direction, and a decollimation lens positioned between thefirst light source and the HOE, the decollimation lens to decollimatethe first beam of light.

Example 22 includes the system as defined in example 21, wherein a focallength of the decollimation lens defines a focal point for chief rays ofsub-images to be reflected off the HOE from a projector.

Example 23 includes the system as defined in example 22, wherein thedecollimation lens is a diverging lens, the diverging lens positionedbetween the focal point for the chief rays and the HOE.

Example 24 includes the system as defined in example 23, wherein thesecond beam of light is to converge towards a second focal point, thesecond focal point defining a location for the projector.

Example 25 includes the system as defined in example 22, wherein thedecollimation lens is a converging lens, the HOE positioned between thefocal point for the chief rays and the converging lens.

Example 26 includes the system as defined in example 25, wherein thesecond beam of light is to diverge outward from a second focal point,the second focal point defining a location for the projector.

Example 27 includes the system as defined in any one of examples 22-26,further including a lens array positioned between the decollimation lensand the HOE, the lens array to focus separate portions of the first beamof light to separate focal points on a focal plane between the focalpoint for the chief rays and the HOE.

Example 28 includes a method comprising positioning a decollimation lensadjacent to a holographic optical element (HOE), transmitting a firstbeam of light through the decollimation lens towards a first side of theHOE, and transmitting a second beam of light towards a second side ofthe HOE

Example 29 includes the method as defined in example 28, defining afocal point for chief rays of sub-images to be reflected off the HOEfrom a projector based on a focal length of the decollimation lens.

Example 30 includes the method as defined in example 29, furtherincluding positioning the decollimation lens between the focal point forthe chief rays and the HOE, the decollimation lens being a diverginglens.

Example 31 includes the method as defined in example 30, wherein thesecond beam of light is to converge towards a second focal point, themethod further including defining a location for the projector based ona location of the second focal point.

Example 32 includes the method as defined in example 29, furtherincluding positioning the HOE between the focal point for the chief raysand the decollimation lens, the decollimation lens being a converginglens.

Example 33 includes the method as defined in example 32, wherein thesecond beam of light is to diverge from a second focal point, the methodfurther including defining a location for the projector based on alocation of the second focal point.

Example 34 includes the method as defined in any one of examples 29-33,further including positioning a lens array between the decollimationlens and the HOE to focus separate portions of the first beam of lightto separate focal points on a focal plane between the focal point forthe chief rays and the HOE.

Although certain example methods, apparatus and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe claims of this patent.

What is claimed is:
 1. An augmented reality (AR) device comprising: aholographic optical element (HOE) including a recorded optical function;and a projector to emit light toward the HOE, the HOE to reflect thelight based on the optical function to produce a full imagecorresponding to content perceivable by a user viewing the reflectedlight from within an eyebox, a first portion of the content viewablefrom a first location within the eyebox, a second portion of the contentviewable from a second location within the eyebox, the first portionincluding different content than the second portion that isnon-repeating between the first and second portions.
 2. The AR device asdefined in claim 1, wherein the full image is composed of portions ofthe light associated with different ones of a plurality of sub-images,the HOE to reflect the light based on the optical function so that chieflight rays for the plurality of sub-images converge to a focal point,the eyebox located between the focal point and the HOE.
 3. The AR deviceas defined in claim 2, wherein a first sub-image of the plurality ofsub-images includes the first portion of the content of the full imageand a second sub-image of the plurality of sub-images includes thesecond portion of the content.
 4. The AR device as defined in claim 3,wherein the first sub-image and the second sub-image include a sameportion of the full image.
 5. The AR device as defined in claim 1,wherein the HOE is transparent.
 6. The AR device as defined in claim 1,further including: a frame wearable by the user, the frame to supportthe projector; and an eyepiece lens within the frame, the HOE positionedon the eyepiece lens.
 7. An augmented reality (AR) device comprising: aprojector to project light associated with first and second sub-images;and a holographic optical element (HOE) including an optical functionrecorded therein, the HOE to reflect the first and second sub-imagestoward an eyebox based on the optical function, the first sub-imageincluding first content corresponding to a first portion of a full imageperceivable by a user from the eyebox, the second sub-image includingsecond content corresponding to a second portion of the full image, thefirst sub-image not including the second content.
 8. The AR device asdefined in claim 7, wherein the full image is composed of portions ofthe light associated with the first and second sub-images.
 9. The ARdevice as defined in claim 7, wherein the HOE is to reflect the lightbased on the optical function so that chief light rays for the first andsecond sub-images converge to a point behind a pupil of the user viewingthe full image from the eyebox.
 10. The AR device as defined in claim 7,wherein both the first and second sub-image include third contentcorresponding to a third portion of the full image.
 11. A systemcomprising: a holographic optical element (HOE); a first light source todirect a first beam of light toward the HOE from a first direction, thefirst beam of light being collimated; a second light source to direct asecond beam of light toward the HOE from a second direction; and adecollimation lens positioned between the first light source and theHOE, the decollimation lens to decollimate the first beam of light. 12.The system as defined in claim 11, wherein a focal length of thedecollimation lens defines a focal point for chief rays of sub-images tobe reflected off the HOE from a projector.
 13. The system as defined inclaim 12, wherein the decollimation lens is a diverging lens, thediverging lens positioned between the focal point for the chief rays andthe HOE.
 14. The system as defined in claim 13, wherein the second beamof light is to converge towards a second focal point, the second focalpoint defining a location for the projector.
 15. The system as definedin claim 12, wherein the decollimation lens is a converging lens, theHOE positioned between the focal point for the chief rays and theconverging lens.
 16. The system as defined in claim 15, wherein thesecond beam of light is to diverge outward from a second focal point,the second focal point defining a location for the projector.
 17. Thesystem as defined in claim 12, further including a lens array positionedbetween the decollimation lens and the HOE, the lens array to focusseparate portions of the first beam of light to separate focal points ona focal plane between the focal point for the chief rays and the HOE.18. A method comprising: positioning a decollimation lens adjacent to aholographic optical element (HOE); transmitting a first beam of lightthrough the decollimation lens towards a first side of the HOE; andtransmitting a second beam of light towards a second side of the HOE.19. The method as defined in claim 18, defining a focal point for chiefrays of sub-images to be reflected off the HOE from a projector based ona focal length of the decollimation lens.
 20. The method as defined inclaim 19, further including positioning the decollimation lens betweenthe focal point for the chief rays and the HOE, the decollimation lensbeing a diverging lens.
 21. The method as defined in claim 20, whereinthe second beam of light is to converge towards a second focal point,the method further including defining a location for the projector basedon a location of the second focal point.
 22. The method as defined inclaim 19, further including positioning the HOE between the focal pointfor the chief rays and the decollimation lens, the decollimation lensbeing a converging lens.
 23. The method as defined in claim 22, whereinthe second beam of light is to diverge from a second focal point, themethod further including defining a location for the projector based ona location of the second focal point.
 24. The method as defined in claim19, further including positioning a lens array between the decollimationlens and the HOE to focus separate portions of the first beam of lightto separate focal points on a focal plane between the focal point forthe chief rays and the HOE.